Leakage inhibiting supporting structure



Dec. 14, 1965 R. J. MOENING LEAKAGE INHIBITING SUPPORTING STRUCTURE Filed March 12, 1964 INVENTOR Raberf J. Moe/ring ATTORN EY United States Patent 3,223,772 LEAKAGE INHIBITING SUPPORTING STRUCTURE Robert J. Moening, Ottawa, Ohio, assignor to Sylvania Electric Products Inc., a corporation of Delaware Filed Mar. 12, 1964, Ser. No. 351,376 2 Claims. (Cl. 174-17.05)

This invention relates to an electron discharge device supporting structure and more particularly to improved means for reducing electrical leakage therein.

A common problem associated with electron discharge devices and with electron tubes in particular is that of electrical leakage paths developing between the supporting leads in the stem structure of the device during processing and subsequent life.

In simplified form an electron discharge device comprises an evacuated envelope wherein an electron source with elements for generating and controlling electrons is supported by a stem structure having electrical leads hermetically sealed therein and extended therethrough to provide device connections to associated external circuitry. The leads, or electrical conductors, are generally spaced in closevertical array extending through the stem in a manner tov conserve space and keep the physical size of the structure to a desirable minimum. This compactness often creates a-problem in achieving proper electrical isolation of leads which individually conduct electrical potentials of difierent voltage levels.

During the manufacture and subsequent operation of electron discharge devices, there is a tendency for materials to spuriously sublimate from the heated electron generating structure and collect on the adjacent .stem surfaces. This continued sublimation causes an electrically conductive film to form over the surface of the stem which becomes a detrimental electrical leakage factor interfering with the desired operation of the device. To maintain and insure satisfactory operation, this electrically conductive-film must be eliminated or made discontinuous between the individual leads of the stem.

= In certain types of electron tubes, as for example, in cathode ray tubes, it is conventional to provide beads or increased thickenesses of the stem on the interior surface, at discrete points where the hermetically encompassed leadsem'erge therethro'ugh. A smooth stem bead structure of this nature enehances the reliability of the hermetic bonding of the lead within the stem and improves the rigidity of the stem structure but does not inhibit'the formation of a leakage film thereover. To deter the forming of a continuous film of sublimation materials, a metal shield or eyelet substantially fashioned as a'peaked hat with an axial hole therein is fitted on each of the several leads and fixedly positioned over the respective beads. The umbrella effect of the eyelet on the bead provides means for preventing the formation of a continuous leakage path between leads.

While, for the most part, this is an elfective procedure for reducing leakage, there'are certain inherent disadvantages to the use of eyelets as .aforedescribed. The eyelet-to-lead assembly operation is a compartively slow and costly process. Operator skill and reliability are required to make certain that the eyelets are optimumly positioned as required and subsequently welded with a minimum amount of metallic splatter. The design of the metallic eyelet has a natural diametric breadth which diminishes the spacing between adjacent leads thereby deleteriously etfecting their electrical isolation.

Accordingly, an object of this invention is the provision of a stem which is an improvement over cited prior art.

Another object of this invention is the provision of a stem which inhibits electrical leakage path formation.

Yet another object of this invention is the provision Patented Dec. 14, 1965 of a stem with beads so contoured that electrical leakage path formation is inhibited.

A further object of this invention is the provision of a stem with electrical leakage path inhibition means not requiring costly time consuming assembly operations.

A still further object of this invention is the provision of a stem with electrical leakage path inhibition means made of integral ceramic material which does not deleteriously effect electrical isolation of adjacent leads. The foregoing objects are achieved in one embodiment of the invention by the provision of a stem with substantially mushroom-shaped beads which break up continuously electrical leakage path formations and thus prevent deleterious leakage between leads in the stem of an electron discharge device.

For a better understanding of the present invention, together with other and further objects, advantages and capabilities thereof, reference is made to the following disclosure and appended claims in connection with the accompanying drawings in which:

FIG. 1 is a sectioned view illustrating tthe stem portion of a typical electron discharge device.

FIG. 2 is a sectioned view showing another embodiment of the invention.

Referring to the drawing, there is shown in FIG. 1 a portion of atypical electron discharge device 11 which may be a cathode ray tube though not necessarily limited to such. The envelope portion 13 is hermetically sealed to a substantially disc shaped stem 15 which comprises a wafer member 17 having an interior surface 19 and an exterior surface 21. The wafer member 17 integrally contains a concentrically located sealed exhaust tubulation 23 about which a plurality of spaced electrical conductors or leads 25 are vertically disposed in substantially circular array and hermetically sealed in the wafer member 17 in parallel alignment to extend through both surfaces 19 and 21 thereof. Also, forming an integral part of the wafer member 17 and the interior surface 19 are a plurality of configurated beads 27 each hermetically encompassing a section of leads 25. As aforementioned, a function of the beads is to provide increased glass-to-metal seal area and also to give support and impart rigidity to the leads 25. In this instance, each of the configurated beads is so formed that a circumferential portion of the bead extends laterally to shadow or shield another portion of the bead thereby performing an additional leakage path inhibition function to be fully described later. The interior terminal ends 29 of the leads 25 are suitably disposed for attach ment to the mount structure or electron gun, not shown, from whence sublimation emanates during operation, a portion of which is directed toward the beads 27 and the interior surface 19 of stem 15. It is evident that unless some protection is afforded, sublimation of conductive materials spuriously emanating from the electron gun will result in the formation of leakage paths on the interior surface 19 between the several leads 25 disposed therethrough.

In greater detail, the bead 27 as shown in FIGURE 1 comprises a-base portion 31 wherein the bead structure is integrally joined to the wafer member 17. Above the base portion is the body portion 33 separating the base portion from the terminating top portion 35. All of these portions are integrally formed to bondingly encompass a limited section of each conductor 25.

As illustrated, the configurated bead 27 has a laterally extended top portion 35 contoured to shield both the base portion 31 and the body portion 33 from sublimation products resulting from tube processing and subsequent operation. The laterally extended top portion 35 is diametrically larger than the body portion 33 which provides a general mushroom-like shape to the bead. The top surface of the top portion may be flat, concave, or convex as long as the top portion performs the necessary shielding function to provide a discontinuous leakage path between leads 25.

The re-entrant body portion 33 being shaded or shielded by the diametrically larger top portion 35 effects on each bead a substantially circular area of discontinuity in any sublimation film disposed in that general region. While a substantially mushroom-shaped bead contour is shown and described it is intended that the scope of this invention should include any modification thereof wherein at least one re-entrant portion of the bead structure is shielded from sublimation products by a diametrically larger portion thereabove. In this manner, although not shown, a re-entrant base portion could be topped by diametrically larger body and top portions.

Another embodiment, as illustrated in FIGURE 2, shows the body portion 33' bounded by re-entrant contours 32 and 34 integrally joined to the base and top portions 31 and 35 respectively. The surface of the bead configurated by the plurality of re-entrants inhibits the formation of continuous leakage paths.

The wafer member 17 and the integral beads 27 comprising stem are usually made of a ceramic insulative material such as a lead glass. The electrically conductive leads 25 may be of nickel, tungsten, or other similar commercially available materials that will form a compatible bond with the particular glass utilized for the stem structure. The stem 15 can be manufactured or formed in a single operation on a multi-position stem making machine well known to those skilled in the art. The shape or irregular contour of the configuration insulative beads 27 is formed as desired by molds or other forming means positioned at or near the end of the stem making operation while the bead material is still in a proper fluid or plastic state suitable for discrete shaping.

It is readily apparent from the foregoing description that the invention is a means for inhibiting electrical leakage path formations over the stern surface resulting from sublimation of materials from the electron gun during operation that is an improvement over prior art. Shaping of the configurated beads 27 to form discontinuous leakage path formation contours are effective in inhibiting electrical leakage between leads 25. In addition, the beads 27 being of an insulative ceramic material do not close the spacing between adjacent leads 25 to deleteriously effect their electrical isolation. Also, the beads 27 can be shaped on existing stem making equipment by the simple addition of a proper mold, thereby eliminating the former costly and time consuming eyelet-to-lead welding operation.

While there have been shown and described what are at present considered the preferred embodiments of the invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the scope of the invention as defined by the appended claims.

What is claimed is:

1. A leakage inhibiting supporting stem structure for an electron discharge device comprising:

an insulative wafer member having oppositely disposed interior and exterior surfaces;

a plurality of spaced electrical conductors hermetical- =ly sealed into said member and extended therethrough', and

a plurality of sol... insulative circularly configurated beads providing vertical support for said conductors formed of said wafer member material each having a diametrical base portion integral to said interior surface of said member, a body portion having a smaller diametrica-l dimension thereabove and a laterally extended terminating top portion having a larger diametrica'l dimension than said body and said base portions to form a mushroom-shaped head, all of said portions of each head being sequentially combined and integrally formed of uninterrupted like material continuous from said wafer member to bondingly encompass the total section of each respective conductor contained therein, said plurality of beads each having a combined surface contour wherein said laterally extended top portion provides shielding to said body and base portion of said bead and said wafer member to inhibit electrical leakage thereover.

2. In a cathode ray tube having at least one electron gun, a leakage inhibiting supporting stem structure comprising:

a ceramic wafer member having oppositely disposed interior and exterior surfaces and a sealed exhaust tubulat-ion concentrically located therein;

a plurality of spaced electrical leads vertically disposed in substantially circular array and parallel alignment about said tubulation and hermetically sealed into said member and extended therethrough; and

a plurality of solid ceramic mushroom-shaped beads providing vertical support for said leads for-med of said wafer member material each having a base portion integral to said interior surface of said wafer member, a re-entrant body portion thereabove and a terminating top portion laterally extended to shade said body and said base portions, said top portion being diametrically larger than said body and base portions, all of said portions of each bead being sequentially combined and integrally formed of uninterrupted like ceramic material continuous from said water member to bondingly encompass the total section of each respective lead contained therein, said top portions of said plurality of shaped beads providing shielding to effect a substantially circular area of sublimation discontinuity around each bead and prevent the formation of deleterious leakage paths between leads.

References Cited by the Examiner UNITED STATES PATENTS JOHN F. BURNS, Primary Examiner. LARAMIE E. ASKIN, Examiner, 

1. A LEAKAGE INHIBITING SUPPORTING STEM STRUCTURE FOR AN ELECTRON DISCHARGE DEVICE COMPRISING: AN INSULATIVE WAFER MEMBER HAVING OPPOSITELY DISPOSED INTERIOR AND EXTERIOR SURFACES; A PLURALITY OF SPACED ELECTRICAL CONDUCTORS HERMETICALLY SEALED INTO SAID MEMBER AND EXTENDED THERETHROUGH; AND A PLURALITY OF SOLID INSULATIVE CIRCULARLY CONFIGURATED BEADS PROVIDED VERTICAL SUPPORT FOR SAID CONDUCTORS FORMED OF SAID WAFER MEMBER MATERIAL EACH HAVING A DIAMETRICAL BASE PORTION INTEGRAL TO SAID INTERIOR SURFACE OF SAID MEMBER, A BODY PORTION HAVING A SMALLER DIAMETRICAL DIMENSION THEREABOVE AND A LATERALLY EXTENDED TERMINATING TOP PORTION HAVING A LARGER DIAMETRICAL DIMENSION THAN SAID BODY AND SAID BASE PORTIONS TO FORM A MUSHROOM-SHAPED BEAD, ALL OF SAID PORTIONS OF EACH BEAD BEING SEQUENTIALLY COM- 